feat: add docker-compose and deployment guide

[avlebedinsky]

Summary

• Add docker-compose.yml for simplified deployment using .env variables
• Add DEPLOY.md with step-by-step deployment instructions
• Credentials path is configurable via CLAUDE_CREDENTIALS_PATH env var (cross-platform)
• Proxy support via HTTP_PROXY / HTTPS_PROXY env vars

Test plan

• docker compose up -d starts the container successfully
• Bot responds in Telegram private chat
• Bot responds in group chat after adding group ID to whitelist

🤖 Generated with Claude Code

[nickalie]

Most of the content here (Telegram bot setup, finding chat IDs, adding groups to whitelist) already exists in README.md. Having it in two places means they'll inevitably drift apart. I'd suggest removing DEPLOY.md and adding a Docker Compose section directly to README.md instead. The compose file and the few compose-specific notes (skills persistence, proxy config) are the only truly new content — everything else is a subset of what the README already covers

[nickalie]

README.md — The :ro removal from credentials volume mounts is already on main (ef66f97), so those changes can be dropped from this PR